Chinese perch are one of the most valuable food ®sh in China, but the sole source of feed for intensive culture is live prey ®sh. Our previous studies on systematic sensory physiology revealed that this species have a mechanism for this peculiar feeding habit. In the present study, a speci®c training procedure was designed, and both experimental (initial body weight 171.0 g; 120 days) and commercial (initial body weight 52.4 g; 240 days) netcage cultures were conducted to investigate the training success, growth performance and survival of the trained yearlings fed with nonlive or Oregontype moist diet. The training successes of minced prey ®sh and the Oregon moist diet were 100 and 89.9%, respectively, in experimental culture, and 92.2 and 83.5% in commercial culture. In an experimental trial, the ®sh fed minced prey ®sh or the Oregon moist diet attained ®nal body weights of 472.7 g or 344.7 g, although the speci®c growth rates of these groups were signi®cantly lower than that of the ®sh fed live prey ®sh (®nal body weight 560.0 g). Mortality was not signi®cantly related to dietary treatment. In commercial culture, the ®nal body weights were as follows: 750 g on live prey ®sh, 705 g on minced prey ®sh and 651 g on the Oregon moist diet. Feed costs to produce 1 kg ®sh were estimated to be US$6.59 for live prey ®sh, US$1.76 for minced prey ®sh and US$2.07 for the Oregon moist diet. The results of the present study con®rmed that sensory modality and associative learning appear to be critical factors in determining food discrimination of Chinese perch, indicating that both minced trash ®sh and Oregon-type moist diet can be substituted for live prey ®sh in intensive commercial production.

No abstract

No abstract

To investigate the molecular mechanism of fish adipocyte differentiation, the three subtypes of PPAR genes (alpha, beta and gamma) were characterized in a marine teleost red sea bream (Pagrus major). The primary structures of red sea bream PPARs exhibited high degrees of similarities to their mammalian counterparts, and their gene expression was detected in various tissues including adipose tissue, heart and hepatopancreas. During the differentiation of primary cultured red sea bream adipocytes, three PPARs showed distinct expression patterns: The alpha subtype showed a transient increase and the beta gene expression tended to increase during adipocyte differentiation whereas the gene expression level of PPARgamma did not change. These results suggest that they play distinct roles in adipocyte differentiation in red sea bream. In the differentiating red sea bream adipocytes, mammalian PPAR agonists, 15-deoxy-Delta(12,14)-prostaglandin J(2), ciglitazone and fenofibrate did not show clear effects on the adipogenic gene expression. However, 2-bromopalmitate increased the PPARgamma and related adipogenic gene expression levels, suggesting the gamma subtype plays a central role in red sea bream adipocyte differentiation and in addition, fatty acid metabolites can be used as modulators of adipocyte function. Thus our study highlighted the roles of PPARs in fish adipocyte differentiation and provided information on the molecular mechanisms of fish adipocyte development.

To investigate the nutritional regulation of lipid metabolism in fish, molecular characterization of lipases was conducted in red sea bream Pagrus major, and the effects of fasting and refeeding on their gene expression was examined. Together with data from a previous study, a total of four lipase genes were identified and characterized as lipoprotein lipase (LPL), hepatic lipase (HL) and pancreatic lipase (PL). These four lipase genes, termed LPL1, LPL2, HL and PL, share a high degree of similarity. LPL1 and LPL2 genes were expressed in various tissues including adipose tissue, gill, heart and hepatopancreas. HL gene was exclusively expressed in hepatopancreas. PL gene expression was detected in hepatopancreas and adipose tissue. Red sea bream LPL1 and LPL2 gene expression levels in hepatopancreas were increased during 48 h of fasting and decreased after refeeding, whereas no significant change in the expression levels of LPL1 and LPL2 was observed in adipose tissue, indicating that LPL1 and LPL2 gene expression is regulated in a tissue-specific manner in response to the nutritional state of fish. HL and PL gene expression was not affected by fasting and refeeding. The results of this study suggested that LPL, HL and PL gene expression is under different regulatory mechanisms in red sea bream with respect to the tissue-specificities and their nutritional regulation.